OWELL - The Rev. D. George Spagnolia forcefully defended himself yesterday against charges that he sexually abused a teenage boy 31 years ago, becoming the only priest of 10 removed from the pulpit in the Archdiocese of Boston this month to defiantly proclaim his innocence.

''I have done nothing,'' the pastor said, evoking sustained applause from his parishioners gathered at St. Patrick's Church in Lowell. ''I demand due process.''

Spagnolia was removed from his pastoral duties last week, four days after his alleged victim notified church officials that he had been assaulted at age 14 when Spagnolia was parochial vicar at St. Francis de Sales Church in Roxbury.

In a letter to Cardinal Bernard F. Law, Spagnolia said he is refusing to resign as St. Patrick's pastor, and he told supportive parishioners yesterday that he will fight all the way to Rome to be reinstated to his full duties.

He condemned archdiocesan policies that he said presume him guilty even as he tries to clear his name. ''For my reputation, for my brother priests serving the people of God in the archdiocese, and for the people, I cannot stand by mute and allow this injustice to continue unchecked,'' he said.

In a statement, the archdiocese said that in removing Spagnolia it was following church policy designed to protect minors from ''morally abhorrent'' behavior.

Donna M. Morrissey, the archdiocesan spokeswoman, last night characterized Spagnolia's removal as temporary, and said he would be reinstated if an investigation exonerates him.

''Our action should not be seen as a conviction of the accused,'' she said in a telephone interview.

Spagnolia called on Suffolk County prosecutors for a swift investigation and said he hoped to be back at the altar by Easter, March 31.

He is one of 10 Roman Catholic priests - and the fourth pastor - who have been removed from service this month after the archdiocese discovered allegations of sexual abuse against them. But Spagnolia is the first to publicly claim that he has been unjustly accused. Law, meeting with a group of priests last week, said seven of the first eight priests he removed this month admitted they were guilty of sexual abuse.

Spagnolia's attorney, Eileen Donoghue, said her client was ''summarily dismissed without any plans for a hearing.'' She said she would press Daniel F. Conley, the Suffolk County district attorney, for a quick investigation into charges she said are baseless.

Asked whether Spagnolia would agree to be interviewed by investigators, Donoghue replied: ''I need to talk to him about that.''

Morrissey said in a statement that Spagnolia has rights under canon law to challenge the church's decision to remove him. ''It is our obligation as a church and as a community, legally and morally, to fully investigate all allegations of abuse of a minor,'' she said.

David A. Procopio, a spokesman for Conley, said the archdiocese notified Suffolk County prosecutors on Friday about the alleged abuse by Spagnolia which, it said, occurred in Roxbury and Brighton in 1971. The alleged victim was identified only as a 14-year-old male. Spagnolia is accused of molesting him twice, according to the priest's lawyer.

''We don't, at this point, have enough information to go forward,'' Procopio said. ''We have requested from the archdiocese the names of all victims and all records that the archdiocese has pertaining to these allegations. We have not received any of that yet.''

Prosecutors do not know the name of the alleged victim, he said; Spagnolia told reporters that he learned the name of his accuser from the archdiocese.

Spagnolia said, ''The archdiocese provided me with the name and I would be surprised if the archdiocese hadn't turned the name over by now.

''I don't want to say anything else or he will be going through what I am going through.''

The Rev. Thomas F. Clark, pastor of St. Francis de Sales-St. Philip Church in Roxbury, said he had little information about the allegation. ''We're very sad about this,'' he said. ''And we're praying for everybody involved.''

A charge of sexual abuse stemming from an alleged incident that occurred 31 years ago would probably fall outside the statute of limitations. ''But we would investigate anyway to determine that,'' said Procopio.

Speaking in front of the altar, Spagnolia mounted his passionate defense before more than 1,100 people, including several off-duty public safety officers, many of whom wore purple ribbons as a sign of solidarity with their displaced pastor.

He called the archdiocese's new ''zero-tolerance'' policy of removing priests who have been credibly accused of sexual misconduct ''fraudulent'' and he suggested that Law should consider resigning. ''I and many others believe that this policy is unjust and inherently evil in its implementation - for not only does it deny the very foundation of the individual's relationship to society, namely innocent until proven guilty, but also this policy dismisses summarily the code of canon law as it pertains to priests and, more specifically, the removal of pastors,'' he said.

Providing a window into the world of clergy under suspicion, Spagnolia said he received a telephone call from Law's personnel office last Tuesday and was told to report to the chancery the next day. Hours later, Law's personnel secretary detailed the allegations.

''I was told that I must be out of St. Patrick's rectory that very day and that my ability to exercise priestly ministry was taken away,'' Spagnolia said. ''But even more devastating was the knowledge that I will never be assigned to minister as a priest in the Archdiocese of Boston. All of this without due process.''

He said he will obey Law's command that he no longer celebrate Mass. He said he intends to continue to live in St. Patrick's rectory and receive his monthly stipend.

Spagnolia spoke from a prepared text for 20 minutes and then took questions from reporters. He said he is prepared to take his case all the way to the Vatican. Asked whether Law should resign, he replied: ''I must give His Eminence the benefit of the doubt. I am sure he is doing what he thinks is best for the church. But if I, as a pastor, had lost my credibility in my parish, I would resign. Any person who is in a position of responsibility has to look at the credibility quotient and then make that decision.''

Spagnolia said he has received calls of support from many ''brother'' priests, some of whom have also been similarly accused, but no one else has indicated they are prepared to fight their dismissal.

The Rev. Stephen Pointras, now assigned to St. Michael's Church in Hudson, said he came back to his childhood parish yesterday to support Spagnolia because he was a model to young clerics like him.

''I think Spags has always had a good sense of justice and injustice. He is a man of courage and conviction,'' said Pointras.

The Rev. Timothy Kapsalis, pastor of the nearby Holy Trinity Greek Orthodox Church, said, ''I am here because what this man has been through is simply not fair. It takes a whole life to build a reputation and just a minute to break it down.''

Ordained in 1964, Spagnolia's priesthood has been an unconventional one. In 1971, the same year he is accused of sexual abuse, he ended a fast and prayer vigil outside the residence of Cardinal Humberto S. Medeiros after getting an assurance that the archdiocese would build a parochial school at St. Francis de Sales.

He began a 20-year leave from the priesthood beginning in 1973 after a disagreement with Medeiros that he said was centered around the church's race policy.

''It had to do with black-white relations,'' he said yesterday.

Spagnolia did not elaborate.

The Rev. Anthony Nguyen, who has been with the parish as the pastor of its Asian congregation for 16 years, will fill in for Spagnolia on an interim basis.

The church, located in Lowell's Acre section, is one of the poorest in the city, serving about 900 families, with 350 members Vietnamese and Cambodians. The church is in the midst of a $1.4 million renovation project. ''So far we have raised three-quarters of a million, which is totally due to Father Spag,'' said Thu Vu, 36. ''He is the one that has encouraged us each week to make our church and our own lives better.''